壳聚糖超声可控降解及降解动力学研究

通过正交实验法考察了壳聚糖溶液浓度、反应温度、超声强度以及醋酸溶液浓度对超声降解反应的影响,确定了最佳反应条件,制备了一系列不同分子量的壳聚糖.研究了壳聚糖溶液浓度、反应温度以及壳聚糖原料分子参数与降解速率常数的关系.通过红外光谱、X-射线衍射和凝胶渗透色谱对降解产物进行了表征.结果表明,超声降解壳聚糖的最佳条件为10℃,壳聚糖溶液浓度2.5g/L.降解速率常数随壳聚糖溶液浓度和反应温度的降低而增大.高分子量和低脱乙酰度的壳聚糖原料有较高的降解速率和降解速率常数,壳聚糖原料的分子量对降解速率和降解速率常数的影响大于脱乙酰度对其的影响.超声波导致了壳聚糖分子量的降低和产物晶体结构的破坏,但没有改变产物的脱乙酰度和糖残基结构.     

壳聚糖在水溶液中的辐射降解反应

研究了壳聚糖在CH3COOH/NaCl缓冲溶液均相体系下的辐射降解反应,给出了H2O2、异丙醇、pH、样品初始分子量等因素对壳聚糖降解的影响,探讨了实验条件下溶液中不同自由基对壳聚糖降解的作用,并对辐照前后壳聚糖的结构进行了表征.结果表明,酸性条件下,壳聚糖的降解主要由.H和.OH自由基共同作用引起,加入H2O2或者通入N2O都能够略微提高.OH自由基浓度,对壳聚糖的降解有促进作用.加入异丙醇后,由于同时降低了.H和.OH自由基浓度,导致壳聚糖降解缓慢.当溶液的pH接近中性后,对壳聚糖的降解起主要作用的为.OH自由基,加入H2O2或者通入N2O都会增加.OH自由基的浓度,从而明显提高壳聚糖的降解速率.此外,研究发现低分子量的壳聚糖具有较快的降解速率.样品的UV、FTIR分析表明,辐照后除在壳聚糖分子链端生成羰基外,壳聚糖主链结构未见变化,脱乙酰度也没有显著改变,显示出辐射降解是一种有效的控制壳聚糖分子量方法.     

Cu(Ⅱ)对壳聚糖的配位控制降解

对壳聚糖进行液态均相络合反应制得壳聚糖铜配合物,IR、UV、元素分析及热重分析等检测证实了壳聚糖铜配合物中配位键的存在,且显示壳聚糖在形成配位结构后存在有利于降解的优势构象。以H₂O₂对壳聚糖-Cu(Ⅱ)络合物及壳聚糖进行氧化降解,考察降解过程中粘度的变化及降解产物分子量分布,在相同的降解条件下,壳聚糖铜配合物的降解速度明显高于壳聚糖,降解产物分子量分布较壳聚糖直接降解窄,结果进一步证明壳聚糖铜配合物中存在有利于降解的优势结构,同时证明以金属离子Cu(Ⅱ)对壳聚     

用GPC研究壳聚糖氧化降解过程中的分子量及其分布

用凝胶渗透色谱法跟踪研究了过氧化氢对壳聚糖氧化降解过程中壳聚糖的分子量及其分布的影响,结果表明,反应温度、时间和过氧化氢用量对壳聚糖的降解程度及降解产品质量均有影响。     

凝胶渗透色谱法研究壳聚糖生物材料酶降解过程的均匀性

壳聚糖是一种重要的生物医用材料,脱乙酰度是影响其生物降解性能的重要因素。运用凝胶渗透色谱研究了脱乙酰 度及相对分子质量分布相似、而聚合单元N-乙酰氨基-D-葡萄糖和D-氨基葡萄糖分布不同的两种壳聚糖材料在溶菌酶作用 下的降解过程,分析检测了壳聚糖材料在降解过程中的重均相对分子质量、相对分子质量多分散性和相对分子质量分布 的变化。发现聚合单元为随机分布的壳聚糖样品,其降解是均匀的;而聚合单元为段状分布的壳聚糖样品,其降解是非 均匀的;表明其聚合单元的分布方式决定壳聚糖材料酶降解过程的均匀性。     

氧化降解壳聚糖铜配合物制备低聚壳聚糖

氧化降解壳聚糖铜配合物制备低聚壳聚糖;壳聚糖铜配合物;壳聚糖;氧化降解;催化     

羧甲基壳聚糖基生物医用材料降解代谢行为的研究进展

作为一种水溶性多糖高分子材料,羧甲基壳聚糖(carboxymethyl chitosan, CMCTs)具有优异的生物相容性和生物降解性以及保湿、止血、抗菌、可吸收等一系列优良的功能特性,因而被广泛应用于医工交叉领域。羧甲基壳聚糖进入体内后,在酶、氧、微生物、水等环境适宜时能够被降解,并经吸收、代谢、排泄。其体内降解速率主要取决于材料的尺寸、脱乙酰度、取代度、分子量等。了解羧甲基壳聚糖在动物体内的降解代谢行为,对羧甲基壳聚糖在转化过程中的质量控制和临床应用至关重要。然而就目前而言,羧甲基壳聚糖在生物体内降解代谢的影响因素及其体内吸收、分布、代谢、排泄规律缺乏系统性总结,这一现状从基础层面严重制约了其在生物医药领域的进一步发展。基于上述问题,本文对近年来羧甲基壳聚糖基生物医用材料的降解、代谢相关研究进行梳理和总结,重点阐述了羧甲基壳聚糖作为可降解材料的生物学特性、降解方式、代谢过程等,系统揭示羧甲基壳聚糖体内降解、代谢的规律,并对植入物尺寸、脱乙酰度、取代度、分子量、交联度及成分比例等影响羧甲基壳聚糖降解速率的主要因素进行归纳,以期为羧甲基壳聚糖基生物医用材料的研发和转化研究提供参考。     

低分子量壳聚糖制备与应用研究进展

低分子量壳聚糖因具有特殊的生物活性而日益受到人们的关注。本文概要介绍了近5年来国内外低分子量壳聚糖的研究进展,包括低分子量壳聚糖的制备方法,如酶降解法、酸水解法、氧化降解法、物理法等,以及低分子量壳聚糖在农业、医药、抗菌、化妆品、食品等方面的应用。     

壳聚糖的配位控制氧化降解及量子化学研究

提出一种新的壳聚糖降解法——金属配位控制氧化降解法，首先对壳聚糖实行人为特异性结构改造，将壳聚糖转化为壳聚糖金属配合物，再以H2O2对配合物进行氧化降解。对比金属配位控制氧化降解和直接氧化降解的反应结果，表明在相同降解条件下，前一种方法的降解速度明显高于后一种方法，且降解产物分子量分布较后者窄。半经验量子化学hyperchem6.01 ZIND0/1模拟计算结果显示，壳聚糖金属配合物高分子链上配位糖元对应的糖苷键比其他糖苷键更容易发生断裂，壳聚糖链断裂优先发生在该位置，降解反应具有更好的选择性和可控性。     

壳聚糖酶的研究进展

壳聚糖酶是最近发现的一种专一性降解壳聚糖的新酶。本文概述了壳聚糖酶的分布,理化性质和固定化情况,综述了它的催化降解特异性和分子学研究进展,对它在植物抗性方面的应用作了简要介绍。     

Preparation of chitosan nanoparticles by spray drying,and their antibacterial activity

Chitosan nanoparticles were prepared from chitosan of different molecular weight by spray drying. The morphology of the particles was characterized by SEM, and size distribution and zeta potential were determined. The effects of chitosan solution concentration, molecular weight of chitosan, and size of the spray dryer nozzles on average size, size distribution and zeta potential of chitosan nanoparticles were investigated. The effects of chitosan nanoparticles and chitosan nanoparticles–amoxicillin complex on Staphylococcus aureus were also tested. The results showed that the average size of chitosan nanoparticles were in the range 95.5–395 nm and zeta potentials were 39.3–45.7 mV, depending on the concentration and molecular weight of the chitosan. The lower the concentration and molecular weight of the chitosan, the smaller the chitosan nanoparticles and the higher the zeta potential. Testing for antibacterial activity against S. aureus indicated that chitosan nanoparticles strongly inhibited growth of the bacteria; the minimum inhibitory concentration, 20 μg/mL, was lower than those of chitosan solution or amoxicillin. The antibacterial capacity of chitosan nanoparticles also depended on the size, zeta potential, and molecular weight of the chitosan. Complexation of chitosan nanoparticles with amoxicillin improved the antibacterial activity of amoxicillin.     

羧甲基壳聚糖在果蔬保鲜中的应用研究进展

综述了羧甲基壳聚糖的特性及其在果蔬的涂膜保鲜中的应用研究进展,讨论了羧甲基壳聚糖的浓度、分子量、pH值、取代度对其特性的影响,介绍了羧甲基壳聚糖对果蔬的涂膜保鲜效果。本文对开发羧甲基壳聚糖在果蔬防腐保鲜方面的应用具有理论指导意义。     

The performance of chitosan layer in Au/n-Si sandwich structures as a barrier modifier

This study focused on the structural, optical and electrical features of chitosan organic layer obtained by spin coating technique both on glass and n-Si substrates. XRD results indicated that chitosan has polycrystalline orthorhombic nature. While optical transmittance spectrum of the chitosan organic layer exhibited an increasing tendency in the visible range, band gap energy value was calculated as 4.23 eV for chitosan by UV–Vis spectrometer. Electrical performance of organic chitosan layer in a Schottky device was studied by fabricating of Au/n-Si and Au/chitosan/n-Si devices. The suitability of Au/chitosan/n-Si sandwich devices in optoelectronic applications were tested under dark and illumination conditions. The Au/chitosan/n-Si sandwich device exhibits good photodiode characteristics. Furthermore, the effect of X-ray radiation doses on the electrical properties of the Au/chitosan/n-Si sandwich device was also investigated. In order to get information about electrical characteristics as a function of X-ray radiation doses, Au/chitosan/n-Si sandwich device was exposed to X-ray radiation in same exposure time and various doses. The results highlighted that the performance of the device with chitosan organic interface layer deteriorated with increasing radiation dose. In addition, the transportation mechanism of chitosan based Schottky device was discussed in details.     

Preparation of chitosan nanoparticles as carrier for immobilized enzyme

This work investigated the preparation of chitosan nanoparticles used as carriers for immobilized enzyme. The morphologic characterization of chitosan nanoparticles was evaluated by scanning electron microscope. The various preparation methods of chitosan nanoparticles were discussed and chosen. The effect of factors such as molecular weight of chitosan, chitosan concentration, TPP concentration, and solution pH on the size of chitosan nanoparticles was studied. Based on these results, response surface methodology was emploved. The results showed that solution pH, TPP concentration, and chitosan concentration significantly affected the size of chitosan nanoparticles. The adequacy of the predictive model equation for predicting the magnitude orders of the size of chitosan nanoparticles was verified effectively by the validation data. Immobilization conditions were investigated as well. The minimum particles size was about 42±5 nm under the optimized conditions. The optimal conditions of immobilization were as follow: one milligram of neutral proteinase was immobilized on chitosan nanoparticles for about 15 min at 40°C. Under the optimized conditions, the enzyme activity yield was 84.3%.     

水溶性壳聚糖降血脂作用的化学机理(Ⅰ)──水溶性壳聚糖及其衍生物对胆酸盐的结合能力研究

通过壳聚糖氧化裂解,制备了分子量为8000的水溶性壳聚糖,并通过烷基化反应合成了二乙氨乙基壳聚糖、二甲氨基(1-甲基)乙基壳聚糖及二乙基甲基铵乙基壳聚糖.在体外测定了水溶性壳聚糖及其衍生物对胆酸盐(牛磺胆酸钠和甘氨胆酸钠)的结合能力及其影响因素.结果表明,水溶性壳聚糖结合胆酸盐的能力主要取决于其阳离子化程度.修饰后的壳聚糖结合胆酸盐的能力增强,说明引入更多的胺基或铵基有利于对胆酸盐的结合.     

粘度法研究壳聚糖与两性聚氨酯胶束间的相互作用

通过粘度法考察了壳聚糖(CS)在盐酸水溶液中与表面带有正电荷的两性聚氨酯(APU)胶束的相互作用，并研究了小分子盐浓度、pH及不同混合方式对复合体系粘度的影响．结果表明：在壳聚糖／APU盐酸混合体系中，较高浓度下APU胶束与壳聚糖分子间的静电斥力作用导致壳聚糖大分子链的伸展，使体系粘度提高，同时降低了壳聚糖溶液对电解质、pH的敏感性；不同混合过程导致壳聚糖大分子构像及其与APU组装、复合形态有很大差别，使混合体系流变性表现出明显的不同．     

Biomimetic modification of chitosan with covalently grafted lactose and blended heparin for improvement of in vitro cellular interaction

Lactose‐ and heparin‐modified chitosan films were prepared and their physical and biological properties were compared with chitosan, chitosan‐g‐heparin, and chitosan‐g‐lactose films. Atomic force microscopy (AFM) measurement showed that all these films in the dry state were rather flat with a roughness smaller than 20 nm. While the chitosan‐g‐lactose/heparin and chitosan‐g‐lactose films have the highest swelling and weight loss ratios, the chitosan and chitosan‐g‐heparin films have the lowest. The chitosan‐g‐lactose/heparin film showed stronger ability to induce chondrocyte attachment, proliferation, viability, and glycosaminoglycan (GAG) secretion than that of the chitosan, chitosan‐g‐heparin, and chitosan‐g‐lactose films. Chondrocyte aggregates and nodules were observed on the chitosan‐g‐lactose/heparin and chitosan‐g‐lactose films, which still preserved viable metabolic ability. These results show that the lactose‐modified and heparin‐incorporated chitosan film can enhance the cell–biomaterial interaction synchronously. The resulting chitosan‐g‐lactose/heparin material is more bioactive that might be applicable as promising scaffold for chondrogenesis. Copyright © 2007 John Wiley & Sons, Ltd.     

Facile fabrication of chitosan active film with xylan via direct immersion

Chitosan film was immersed in NaOH solution with xylan to simply prepare active chitosan/xylan film. FT-IR, XRD, FE-SEM, AFM and XPS were used to evaluate the effects of xylan on the structure and morphology of chitosan film, and a wide variety of material characteristics of the chitosan/xylan composite films were investigated. The results showed that the xylan chains entered into the gap of chitosan film and became nodules, leading to strong hydrogen bonds and electrostatic interactions between chitosan and xylan. Moreover, the introduction of xylan not only resulted in stronger crystallinity and a more compact structure of chitosan film, but also had an important effect on the properties of chitosan film. The tensile strength, breaking elongation and anti-ultraviolet performance of the chitosan/xylan films were improved greatly with the increasing concentration of xylan; the water vapor transmission rate, water absorption rate and oxygen barrier property of chitosan/xylan composite films were higher than those of chitosan film; chitosan/xylan composite films still showed hydrophobicity when the xylan concentration was more than 1 %. The chitosan/xylan composite film has more potential to be used as food packaging than pure chitosan film.     

Selective crystallization of calcium salts by poly(acrylate)-grafted chitosan

The biopolymer chitosan was chemically modified by grafting polyacrylamide or polyacrylic acid in a homogeneous aqueous phase using potassium persulfate (KPS) as redox initiator system in the presence of N,N-methylene-bis-acrylamide as a crosslinking agent. The influence of the grafted chitosan on calcium salts crystallization in vitro was studied using the sitting-drop method. By using polyacrylamide grafted chitosan as substrate, rosette-like CaSO4 crystals were observed. This was originated by the presence of sulfate coming from the initiator KPS. By comparing crystallization on pure chitosan and on grafted chitosan, a dramatic influence of the grafted polymer on the crystalline habit of both salts was observed. Substrates prepared by combining sulfate with chitosan or sulfate with polyacrylamide did not produce similar CaSO4 morphologies. Moreover, small spheres or donut-shaped CaCO3 crystals on polyacrylic acid grafted chitosan were generated. The particular morphology of CaCO3 crystals depends also on other synthetic parameters such as the molecular weight of the chitosan sample and the KPS concentration.     

改性壳聚糖树脂对利尿剂的吸附性能

用琥珀酸酐、苯甲酸酐、聚乙烯亚胺和 3 氯 2 羟丙基三甲基氯化铵对壳聚糖进行改性 ,分别在其氨基上引入羧基、苯环、多氨基和季胺基 ,并利用红外谱图对于改性后的壳聚糖的结构进行了分析 .应用相转移法制备了 4种改性壳聚糖的微球 ,实验研究了这 4种微球对 9种不同利尿剂的吸附性能 .结果表明 ,由于Lewis酸碱相互作用 ,引入羧基后的壳聚糖树脂对 3种碱性利尿剂的吸附量有了 15 %～ 36 %的提高 ,而引入多氨基的壳聚糖树脂对四种酸性利尿剂的吸附量分别提高了 4 8 5 %～ 2 0 9% ;由于苯环和利尿剂的憎水性基团的相互作用 ,引入苯环后的壳聚糖树脂对所有的利尿剂的吸附量都有所提高 ,其幅度为 15 %～ 6 1% ;因为季胺基团和羧基之间发生的离子交换作用 ,引入季胺基后的树脂对具有羧基的利尿剂吸附量有显著的提高 ,尤其对布美它尼的吸附量提高了 2倍以上 .